Lock screen gets magnified and unable to unlock the screen, videos stored manually not being played

I have updated my Lumia 920 to 8.1, from then sometimes my lock screen gets magnified and it would be impossible to unlock as the fullscreen is not viewed. The phone has to be restarted for this always.

Secondary, earlier I used to easily access the videos or movies stored in videos folder, but now if we try playing some videos through VIDEO app it displays a message "signing in....",then "logging in........", but not able to connecct and videos are not being played.